1. Field of the Invention
The field of the invention is that of amplifier bias control systems. The invention applies in particular to power microwave amplifiers with a wide output power dynamic range used in TDMA (Time-Division Multiple Access) signal transmitters and receivers.
The present invention is directed to optimizing the efficiency of an amplifier used to transmit or receive radio signals, for example TDMA signals. It provides a constant amplifier gain by biasing the amplifier so that the signal applied to it is amplified linearly, with minimal power consumption, i.e. with minimal bias. The invention applies to all TDMA signals, regardless of the receive packet length, their amplitude, their dynamic range and their relative timing.
2. Description of the Prior Art
European patent application No 0 472 330 (MATSUSHITA ELECTRIC INDUSTRIAL CO. LTD) describes a system for amplifying a TDMA microwave signal in which a diode detector detects the amplitude of the output signal of an amplifier. This detector cooperates with a digital attenuator receiving the envelope of the amplified signal to increase the sensitivity of the detector on its output side, which in theory is limited to approximately 20 dB. The attenuator is therefore governed by a control law determined beforehand according to the envelope of the signal to be amplified.
The major drawback of this type of system is that it requires a circuit, for example an EEPROM, to generate the envelope of the signal to be amplified. Programming this EEPROM entails a knowledge of the length of the packets received and their relative timing. It is also necessary to use a linearizer in the control system of the amplifier to compensate for the non-linear characteristic of the detector diode.